Method for making filter cartridges

ABSTRACT

AN APPARATUS AND METHOD FOR MAKING FILTER CARTRIDGES WHEREIN DRY, THERMO-SETTING RESINS ARE DISPERSED THROUGHOUT A FIBROUS MASS BY BEING DEPOSITED THEREON, BEAT INTO IT UNTIL THEY ARE SUBSTANTIALLY DISPERSED THROUGHOUT THE   INTERSTICES OF THE FIBROUS MASS, AND THEN THEY ARE THERMOSET BY HEAT.

April 16, 1914 N. mu.

METHOD FOR MAKING F ILTER CARTRIDGES Filed June 1, 1972 ABSTRACT OF THE DISCLOSURE An apparatus and method for making filter cartridges wherein dry, thermo-setting resins are dispersed throughout a fibrous mass by being deposited thereon, beat" into it until they are substantially dispersed throughout the interstices of the fibrous mass, and then they are thermoset by heat.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to apparatus and methods for making filter cartridges, and particularly to apparatus and methods for making filter cartridges wherein finely pulverized dry thermo-setting resinous materials are dispersed throughout a fibrous mass, which is then subjected to heat until the materials are thermo-set.

Description of the prior art Filter cartridges are now ordinarily made by preparing a bath of dissolved thermo-setting resins, then wetting a strip of felt with the solution of the bath until the felt is thoroughly invested with the solution of thermo-setting resin, whereupon the felt is subjected to heat until the felt is dried and the resin is cured and set. Obviously, the amount of heat necessary to drive off the water, which is the vehicle for the resin that invests the felt, is a wasteful expenditure of energy, since that heat takes no part in the formation of the filter cartridge other than to act as a vehicle for the resin. Not only is the heat energy wasted, but considerable amounts of time are wasted to drive off the moisture content. These several factors considerably increase the cost of production of filter cartridges.

SUMMARY OF THE INVENTION It has been found that the unnecessary expenditure of thermal energy and time can be avoided, and that the cartridges can be made in much lesser time by dispensing with the fluid solvent vehicle for the resins according to the conventional technique for impregnating the felt material which is the base of the filter cartridge. Instead of dissolving the resin, the resin is instead deposited upon the top surface of the felt or other material of which filter cartridges is to be made, and is pounded into the felt by beaters. Not only does this drive the finely pulverized dry thermo-setting resins into the interstices of the fibrous material or felt, but at the same time momentarily compresses the felt, and drives the air out of it, only to permit the air to return when pressure on the felt by the heaters is relieved. This accomplishes a more complete dispersion of the finely pulverized dry thermo-setting resins throughout the entire filter body, and produces a product which does not need the wasteful expenditure of thermal energy over a long period of time to drive out the moisture before accomplishing the thermo-setting of the resins.

THE DRAWINGS These objects and advantages as well as other objects and advantages may be attained by the device shown by way of illustration in the drawings in which the figure is a side elevational view of the apparatus for investing a Patented Apr. 16, 1974 fibrous strip with finely pulverized dry thermo-setting resinous material.

- PREFERRED EMBODIMENT In accordance with the present invention, the porous filter cartridge is made in continuous lengths by unrolling a band 11. of felt, or other loose fibrous material of suitable character from a spool 12 and leading it across an anvil 13. As, the band 11 moves across the anvil 13, a hopper 14 discharges from its lower end on to the surface of the band 11, a finely pulverized, or pulverulent dry, thermo-setting resinous material 15. Phenolforrnaldehyde resinsare most suitable for this purpose and there are numerous kinds as, for example, Bakelite (Union Carbide), Durez (Hooker Chemical Co.). The finely pulverized dry thermo-setting resinous material lies on the surface of the band 1.1, which is moving toward a high speed beater 16. The high speed beater 16 is attached to an arm 17 mounted eccentrically to the crank shaft 18 of a motor. The beater 16 repeatedly pounds the resin 15, which penetrates the interstices of the fiber of the band 11. The band 11 is a relatively dense fibrous mass of felt, or other suitable material, and it is compressed by the high speed beater 16 so that any air in the interstices may be momentarily squeezed out during the compression phase, and

allowed to return during the corresponding expansion phase, for the felt is somewhat resilient. The squeezing out of the air, and its return, encourages the penetration of the resin 15 throughout the band 11, and coupled with the beating, accomplishes quite complete and uniform dispersion of dry resinous particles throughout the band. Beating, and a gaseous vehicle (air) has been substituted for the conventional liquid solvent vehicle for dispersing the resinous material throughout the fibrous mass of the filter cartridge. Immediately, since the fibrous material or felt is dry to start off with, the 970 B.t.u.s necessary to drive off each pound of water in the conventional wet method will not be utilized for that purpose, and the heat is immediately devoted entirely to the curing process.

As an example of the typical needle felt that is appropriate for preparing filter cartridges, there is one of 40 den. rayon and 25% 15 den. rayon with a weight of 25 ounces per square yard needled to a thickness of .500 inch; this felt has an air porosity of 300 cubic feet per minute at /2 inch water pressure drop. Porosity of the product can be varied by alteration of any of the example parameters. The resin content can be varied from approximately 40% by weight of the felt, to a very small percentage of resin, or by increasing or decreasing the beat frequency, or by increasing or decreasing the beat energy, or by controlling the rate of deposition of the resin from the hopper 14, or by increasing or decreasing the speed of movement of the band 11.

The resin under heat becomes plastic, flows and invests the material surrounding it by coating individual filaments particularly at their cross over points, where they become linked when the resin polymerizes into an insoluble rigid set form. I

Needle felts tend to collapse and mat down to form a non-porous surface in use. By intersectional bonding, a porous open filtration structure is attained, and the pressure drop across the cartridge is held to a minimum.

Formation of the cartridge from the impregnated material is performed in an oven 30. The strip 11 is drawn from the impregnation station by variable speed feed rollers 31, which pull the strip through the oven 30. The strip 11 is first formed into a cylinder as it moves into a cylindrical guide (not shown) leading it through the oven 30'. Upon departure from the oven, the pulling rollers 31 carry it to a point where the strip 11 may be cut into suitable lengths.

The curing of the cylindrical cartridge in the oven is'con- I ventional, and is not set forth in detail. v I g What is claimed is: 1. A method for making porous filter cartridges comprising:

(a) providing a band of dense, needle felt, (b) depositing the band on a rigid anvil support, (0) depositing a pulverulant, dry, thermo-setting material on the top surface of the band,

((1) beating the band, and the pulverulent material on 1 the top surface of the band, against the rigid anfvil by successive impacts, successively to compress the band against the anvil, and to then allow the band to resiliently expand upon withdrawal of the beater; whereby:

(A) the material lying on the band is driven into the interstices of the band, (B) air is expelled from the interstices of the band repeatedly by compression,

(C) air returns to the interstices of the band as it 20 resiliently expands, carrying some of the material into the interstices, (e) applying heat to set the material.

3,338,996 8/1967 Harris 264-70 2,890,147 6/1959 Pearson et a1 264ll2 3,703,396 11/1972 -Lananche e1.a1., 264 137 ROBERT F. WHITE, Primary Examiner-- G. UVILLE, Assistant Examiner fU-s. c1," XgR. 264-120,137 

